1. Field of Invention
The present invention relates to a manufacturing a transflective display device.
2. Description of the Related Art
Recently, display devices such as the liquid crystal display (LCD) device, plasma display panel (PDP), organic light emitting diode (OLED), and electro phoretic indication display, among others, have been gradually replacing the cathode ray tube (CRT) in various display applications.
A liquid crystal display includes a thin film transistor substrate on which thin film transistors are formed, color filter substrate on which color filters are formed, and a liquid crystal panel having liquid crystal layers inserted between the thin film transistor substrate and the color filter substrate. Since the liquid crystal panel is a non-light-emitting element, a backlight unit is often mounted on a rear surface of the thin film transistor substrate to supply light. The amount of light emitted by the backlight unit that is transmitted through the liquid crystal layer is adjusted according to the arrangement state of the liquid crystal molecules in the layer. By controlling the light transmission, a desired image is displayed on the liquid crystal panel.
The liquid crystal display can be classified into transmission type, reflective type, and transflective type according to the types of used light sources. The transmission-type liquid crystal display allows light (e.g., light from a backlight unit) to pass through the liquid crystal panel, thereby displaying images of a consistently high quality regardless of the amount of light available in the environment. The reflective-type liquid crystal display, in which reflective layers are formed on the entire surface of pixel electrodes, utilizes light in the environment to display images. An advantage of the reflective-type liquid crystal display is that it does not rely on the backlight unit as the sole source of light, thus consuming only about 30% of the amount of power that is consumed by the transmission-type liquid crystal display. A reflective-type liquid crystal display includes reflective layers that reflect the light from the environment and uses the reflected light to display images.
The transflective-type liquid crystal display combines the transmission-type liquid crystal display's ability to consistently produce high-quality images with the reflective-type liquid crystal display's ability to operate at low power consumption. The transflective-type liquid crystal display can implement high picture quality, is small in size, light in weight, and has low power consumption requirement. Particularly, the transflective-type liquid crystal display uses the light in the environment and a backlight unit to ensure a proper brightness level regardless of changes in the environment. Advantageously, this ability to modulate the brightness not only ensures that the images will be adequately bright but also makes adjustments according to lighting conditions. For example, a transflective-type liquid crystal display allows users to view still and moving images as well as character information even under direct sunlight.
When the thin film transistor substrate of the transflective liquid crystal display is manufactured, an organic passivation layer is applied to substantially the entire surface of a mother substrate, concavo-convex pattern is formed using a slit mask in the surface of the organic passivation layer formed on insulating substrate to be used as the thin film transistor substrate, and then pixel electrodes and reflective layers are sequentially formed. The concavo-convex pattern is used to induce diffused reflection and light scattering of the reflective layers.
The concavo-convex pattern may be formed by a half exposure method or a planarization method. The half exposure method entails performing a photolithography process multiple times to form the concavo-convex patterns, contact holes, etc., and thus requires long manufacturing time and high manufacturing cost. As for methods using the slit mask, they cannot induce appropriate diffused reflection and scattering since the yield and reflection efficiency of the concavo-convex patterns are low.
A method of forming the concavo-convex pattern in the thin film transistor substrate without the above problems is desired.